The present application relates generally to lubricants and, more particularly, to improving the quality of lubricants through the addition of high performance lubricant additives that enhance desirable properties of lubricants.
Commercial lubricants are compositions containing a lubricant base such as a hydrocarbon base oil or base grease (oil to which a thickener has been added to form a semi-solid or gel), to which are added various lubricant additives selected for additional desirable properties. Lubricant additives may enhance the lubricity of the lubricant base and/or may provide antiwear, antifriction, or other desirable characteristics.
Lubricants are used in enormous quantities. For example, more than four billion quarts of crankcase oil are used in the United States per year. However, many lubricants currently in use have undesirable side effects. Currently available crankcase oils generally include the anti-wear additive zinc dialkyldithiophosphate (ZDDP), which contains phosphorous and sulfur. This phosphorous and sulfur ends up in the exhaust gas and poisons the catalytic converter causing increased automotive emissions. It is expected that the automotive industry will eventually mandate the total elimination of phosphorous and/or sulfur components in lubricants or will allow only extremely low levels of phosphorous and/or sulfur in crankcase oil. In addition, ZDDP produces ash (inorganic oxides that can be abrasive) due to the presence of zinc. However, no acceptable anti-wear additive to replace ZDDP in engine oils is currently available and thus it is still used, although desirably in smaller amounts.
Accordingly, it is an object of the present invention to provide environmentally friendly anti-wear additives for lubricants, wherein the amounts of phosphorous and sulfur which are contributed by the anti-wear additive to the lubricant are reduced. It is another object of the present invention to provide additives that produce little to no ash content from metal oxide production on combustion. It is yet another objective of the present invention to provide additives with desirable antiwear and antifriction characteristics.
A new class of materials called alkylphosphorofluoridothioates have been developed that exhibit superior wear protection compared to the current additive ZDDP. These materials are ashless because they do not contain metallic elements. In addition, these alkylphosphorofluoridothioates can be used at much lower levels of phosphorous content compared to ZDDP resulting in decreased fouling of the catalytic converters in automobiles and resulting in lower emissions. There is also the potential to reduce friction in the engine resulting in improved fuel economy compared to current additives in the marketplace.
Fluorothiophosphates are disclosed in US Patent Application No. 20060281644, for example. These fluorothiophosphates are produced by reacting a metal fluoride with an organothiophosphate such as ZDDP, yielding a fluorinated organothiophosphate. The reacting step involves heating and milling the reactants. The fluoride displaces one of the sulfur atoms in the reaction.
The present invention is a facile method for preparing alkylphosphorofluoridothioates and an improvement over the additives taught in US Patent Application No. 20060281644 and related applications. The present invention further comprises novel alkylphosphorofluoridothioates, methods of using same as lubricant additives, and lubricants containing the same.